Fabrication Electrochemical Biosensors Based On Nanomaterials

Since the birth of micro-scale especially for nanomaterials, they are a hotspot in research and applications field all the time, which are now in the stage of rapid development. A variety of new nanomaterials with special functions are emerging in an endless stream, which expands further research and applications of these materials. Electrochemical apparatus because of some advantages such as sensitive, simple and easy to operate, good controllability, low cost and easy to be minisized, has received extensive attention. Nowadays, people found that when combining nanotechnology with electrochemical sensing technology, it not only made sensors in a revolutionary development but also promoted the development of nanotechnology. For those reasons, we investigate the preparation of carbon materials and noble metal nanomaterials, with electrocatalytic activity and high biocompatibility, and their applications in electroanalysis and sensing field.(1) In chapter2, a novel DNA-templated Au nanoparticles (Au-DNA) nanoconjugate was prepared by using the combination of metallization and DNA compaction. The electrostatic interaction between Au(Ⅲ) and the phosphate backbone of DNA formed the netlike coordination compound of Au(Ⅲ)-DNA, and then the complex was chemically reduced to form Au nanoparticles in this network-like DNA conformation. The negatively charged nanoconjugate was used as the matrix for immobilization of horseradish peroxidase (HRP). A stable and well-defined redox peaks of HRP were observed on the Au-DNA nanoconjugate modified glassy carbon (GC) electrode, which indicated that the modified enzyme electrode displayed good direct electron transfer behavior and excellent reducing ability toward hydrogen peroxide (H2O2) with the apparent Michaelis-Menten constant (Km) estimated to be0.147mM.(2) In chapter3, a biomorphic carbon, retained its anatomical features, was prepared by carbonizing wood through controlled heated rates. Then Pt particles were electrodeposited onto the synthesized carbon materials. The OPC/Pt composite materials were modified onto the surface of GC electrode by means of chitosan. The modified electrode shows good response to H2O2due to the good electrochemical properties of the hybrid.(3) In chapter4, natural basswood biomorphic porous carbon (BBPC) materials with unidirectional ordered pores have been successfully prepared by carbonization in an inert atmosphere. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) were employed to characterize the phase identification, microstructure and morphology analysis. The carbon materials were used to fabricate biosensor to detect hydrogen peroxide (H2O2) without any assistance of enzymes because of their satisfying electrocatalytic properties. It was immobilized on glassy carbon electrode (GCE) with chitosan (CHIT) to fabricate a new kind of biosensor, BBPC/CHIT/GCE, which showed excellent electrocatalytic activity to the reduction of H2O2. Meanwhile, BBPC also could promote electron transfer with the help of hydroquinone. The simple and low-cost biosensor exhibited high sensitivity, good operational and long-term stability.(4) In chapter5, a novel electrogenerated chemiluminescence (ECL) biosensor using gold nanoparticle as signal transduction probes was described for the detection of kinase activity. The gold nanoparticles were specifically conjugated to the thiophosphate group after phosphorylation process in the presence of adenosine59-[y-thio] triphosphate (ATP-y-s) co-substrate. Due to its good conductivity, large surface area and excellent electroactivity to luminol oxidization, the gold nanoparticles extremely amplified the ECL signal of luminol, offering a highly sensitive ECL biosensor for kinase activity detection. Protein kinase A (PKA), an important enzyme in regulation of glycogen, sugar and lipid metabolism in human body, was used as a model to confirm the proof-of-concept strategy. The as-proposed biosensor presented high sensitivity, low detection limit of0.07U mL"1, wide linear rang (from0.07to32U mL"1) and excellent stability. Moreover, this biosensor can also be used for quantitative analysis of kinase inhibition. Based on the inhibitor concentration dependent ECL signal, the half-maximal inhibition value IC50of ellagic acid, a PICA inhibitor, was estimated, which was in agreement with those characterized with conventional kinase assay. While nearly no ECL signal change can be observed in the presence of Tyrphostin AG1478, a tyrosine kinase inhibitor but not PKA inhibitor, showing its excellent performance in kinase inhibitor screening.(5) In chapter6, we reported a novel cathodic electrogenerated chemiluminescence (ECL) of luminol at a positive potential (ca.0.05V vs. Ag/AgCl) with a strong light emission on the graphene modified glass carbon electrode. The resulted graphene modified electrode offers an excellent platform for high performance biosensing applications. Based on the cathodic ECL signal of luminol on the graphene modified electrode, an ECL sandwich immunosensor for sensitive detection of cancer biomarkers at low potential was developed with a multiple signal amplification strategy from functionalized graphene and gold nanorods multilabeled with glucose oxidase (GOx) and secondary antibody (Ab2). The functionalized graphene improved the electron transfer on the electrode interface and was employed to attach the primary antibody (Abi) due to it large surface area. The gold nanorods was not only used as carrier of secondary antibody (Ab2) and GOx but also catalyzed the ECL reaction of luminol, which further amplified the ECL signal of luminol in the presence of glucose and oxygen. The as-proposed low potential ECL immunosensor exhibited high sensitivity and specificity on the detection of prostate protein antigen (PSA), a biomarker of prostate cancer that was used as a model. A linear relationship between ECL signals and the concentrations of PSA was obtained in the range from10pg mL-1to8ng mL-1. The detection limit of PSA was8pg mL-1(signal-to-noise ratio of3). Moreover, the as-proposed low potential ECL immunosensor exhibited excellent stability and reproducibility. The graphene based ECL immunosensors accurately detected PSA concentration in10human serum samples from patients demonstrated by excellent correlations with standard chemiluminescene immunoassay.